Direct competitive fluoroimmunoassays for detection of imidaclothiz in environmental and agricultural samples using quantum dots and europium as labels

- QDFIA and TRFIA were developed and applied to the monitoring of imidaclothiz.
- QDFIA and TRFIA showed higher sensitivity than reported ELISA and FPIA.
- Eight kinds of matrix were studied by spiked recovery experiment.
- The amounts of imidaclothiz in real samples detected by QDFIA and TRFIA were correlated with that detected by HPLC.

A direct quantum dots-based fluoroimmunoassay (QDFIA) and a time-resolved fluoroimmunoassay (TRFIA) for imidaclothiz (IMI) were developed by using the quantum dots (QDs)-labeled antibody and the europium (Eu3 +)-labeled antibody, respectively. After optimization, the half-maximal inhibition concentration (IC50) and the limit of detection (LOD, IC10) are 20.41 and 0.52 μg L− 1 for the QDFIA, while 6.91 and 0.018 μg L− 1 for the TRFIA, respectively. The cross-reactivities (CRs) with the analogues are negligible except for imidacloprid with CRs of 29.0% for the QDFIA and 26.6% for the TRFIA. The spiked recoveries of IMI in paddy water, soil, pear, tomato, rice, apple, cabbage and cucumber are 72.7-117.6% with a standard deviation (RSD) of 2.4- 13.5% for the QDFIA, and 81.3-117.7% with a RSD of 1.6- 7.5% for TRFIA. The detection results of the analyses for the real paddy water and pear samples are markedly correlated with these of high-performance liquid chromatography (HPLC).

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